Cardiac Ultrasound
Screening cardiac ultrasound evaluation is limited to the detection of cardiac activity in patients with pulseless electrical activity and the detection of pericardial effusion/tamponade.
PEA is defined as the presence of electrical cardiac activity in the absence of pulses. This does not necessarily mean that the heart is not beating. Multiple reasons relating to low-flow states including hypovolemia, peripheral vascular disease, tamponade, and tension pneumothorax may contribute to this finding. Simple rapid visualization of the heart wall allows the physician to assess for activity. If cardiac activity is discovered then rapid evaluation and correction of the low flow state may be life-saving.
Pericardial tamponade, although discussed in more detail in the trauma ultrasound review, certainly may and does occur in medical patients. Causes of this sometimes life-threatening diagnosis may include uremic pericardial effusion, pericardial effusion status post cardiac surgery or pericarditis. With the exception of hypotension, a patient's body habitus often makes the detection of muffled heart sounds and distended neck veins as per Beck's triad clinically difficult to appreciate. Rapid bedside ultrasound provides the Emergency Physician with the ability to quickly diagnose the presence of an effusion prior to onset of tamponade physiology (Figure 5). This event is marked sonographically by the collapse of the right atrial and/or ventricular walls during diastole. Obviously, in the right clinical setting, simple detection of pericardial fluid is enough to initiate immediate treatment. An example of this is the patient who is found in PEA. Normally, peri-cardiocentesis is a last effort in a presumably futile resuscitation. Intuitively, with early detection and correction of tamponade, a patient's chance of survival greatly increases.